code: def update(self, aggr_out):
      return aggr_out
  
file_path: pytorch_geometric/test/nn/conv/test_create_gnn.py
imports: import torch
  from torch_geometric.nn import MessagePassing
  from torch_geometric.utils import add_self_loops, degree
label_desc: Use image node_id 4 for calling the GCNConv obj's underlying member method code with example usage: obj.update(aggr_out) and returns: aggr_out